A circuit interrupter is an electrical component that can break an electrical circuit, interrupting the current. A basic example of a circuit interrupter is a switch, which generally consists of two electrical contacts in one of two states; either closed meaning the contacts are physically touching and electrical current passes from one contact to the other, or open, meaning the contacts are separated relative to each other, thereby preventing the flow of electrical current therebetween. A switch may be directly manipulated by a person as a control signal to a system, such as a computer keyboard button, or to control power flow in a circuit, such as a light switch.
A second example of a circuit interrupter is a circuit breaker. A circuit breaker is generally used in an electrical panel that monitors and limits the amount of current (amperage) being sent through the electrical wiring. A circuit breaker is designed to protect an electrical circuit from damage caused by an overload or a short circuit. If a power surge occurs in the electrical wiring, the breaker will trip. This will cause a breaker that was in the “on” position to flip to the “off” position and shut down the electrical power leading from that breaker. When a circuit breaker is tripped, it may prevent a fire from starting on an overloaded circuit; it can also prevent the destruction of the device that is drawing the electricity.
A standard circuit breaker has a line terminal and a load terminal. Generally, the line terminal is in electrical communication with a supply of incoming electricity, most often from a power company or generator. This can sometimes be referred to as the input into the circuit breaker. The load terminal, sometimes referred to as the output, feeds out of the circuit breaker and connects to the electrical components being fed from the circuit breaker. There may be an individual component connected directly to a circuit breaker, for example only an air conditioner, or a circuit breaker may be connected to multiple components through a power wire which terminates at electrical outlets.
A circuit breaker can be used as a replacement for a fuse. Unlike a fuse, which operates once and then has to be replaced, a circuit breaker can be reset (either manually or automatically) to resume normal operation. Fuses perform much the same duty as circuit breakers, however, circuit breakers are safer to use than fuses and easier to fix. If a fuse blows, oftentimes a person will not know which fuse controls which specific power areas. The person will have to examine the fuses to determine which fuse appears to be burned or spent. The fuse will then have to be removed from the fuse box and a new fuse will have to be installed.
Circuit breakers are much easier to fix than fuses. When a circuit breaker trips, one can easily look at the electrical panel and see which breaker handle has moved to the tripped position. The circuit breaker can then be “reset” by turning the handle to the “off” position, and then moving the handle to the “on” position.
In general, a circuit breaker has two contacts located inside of a housing. The first contact is typically stationary, and may be connected to either the line terminal or the load terminal (often, the line terminal). The second contact is typically movable with respect to the first contact, such that when the circuit breaker is in the “off”, or tripped position, a physical gap exists between the first and second contacts. The second contact may be connected to whichever of the line terminal or the load terminal that the first contact is not connected to (often, the second contact is connected to the load terminal).
To trip the circuit breaker so as to open the circuit, an overcurrent sensor may be provided (such as, for example, a hydraulic magnetic overcurrent sensor or a thermal overcurrent sensor) or a solenoid type trip mechanism with an overcurrent sensor may be used. When the overcurrent sensor senses a current level above a threshold level, which may, for example, be a percentage above the rated current of the circuit breaker, the overcurrent sensor or solenoid may be actuated to mechanically move the second contact away from the first contact, thereby tripping the circuit breaker to open the circuit.
A problem with a traditional circuit interrupter, however, is that even though it may be in the open position, i.e. a switch is open or a circuit breaker has tripped, interrupting the connection, the open area between the first and second contact allows an electrical arc to form between the two contacts, particularly right as the contacts are opening, or just prior to their closing. The electrical arc may have a high voltage and/or amperage, and as such can be dangerous; they can cause damage to the circuit interrupter, specifically damaging the electrical contacts, linkages or other moveable components. Any damage to the electrical contacts or other components shortens the lifespan of the circuit interrupter and affects its performance.
Another effect of arcing stems from the extremely high temperature of the arc (perhaps tens of thousands of degrees Celsius), which can impact the surrounding gas molecules creating ozone, carbon monoxide, and other dangerous compounds. The arc can also ionize surrounding gasses, potentially creating alternate conduction paths.
Because of these detrimental effects, it has been recognized to be very important to quickly cool and quench the arc in order to prevent damage to the circuit interrupter and/or to limit the above-described dangerous situations.
There have been many proposed devices to quickly quench an arc. For example, U.S. Pat. No. 5,731,561 to Manthe et al. discloses a device with a sealed arc chamber. Inside of the sealed arc chamber is a gas designed to quench the arc that is formed when the circuit breaker trips. A disadvantage of this device is that it may be expensive to produce. The circuit breaker requires a sealed chamber, which may be expensive to manufacture and test, and also requires a specific, arc quenching, gas. The combination of the sealed chamber and the gas make this device relatively expensive. Additionally, any leaks in the chamber will cause a leak in the gas, preventing any quenching from taking place.
U.S. Pat. No. 6,717,090 to Kling et al. discloses a device with an arc splitter stack into which the arc passes via guide rails. A disadvantage of the device proposed in Kling is that it may not quench the arc as rapidly as is desired. While providing some quenching using the arc splitter, the arc splitter alone may not provide enough cooling to quickly quench the arc.
Many other references have also attempted, with varying degrees of success, to increase the rate at which arcs, once created, are quenched.
However, it may be desirable, instead of focusing on the quenching of an arc after it is created, to instead focus on reducing the magnitude and duration of arc creation to begin with. This can be accomplished, for example, by increasing the rate at which the contacts are opened or closed, particularly at the time where the contacts are still relatively close to one another (i.e., just after opening or just prior to coming into physical contact during closing). In general, the faster that the contacts can be opened or closed, the smaller the arc. Moreover, in addition to increasing the rate at which the contacts are opened or closed, it may also be desirable to increase the force with which the contacts engage one another when closed, thereby ensuring satisfactory electrical communication between the contacts.